Timing chain rattle on warm start

[unclegrouch]

I wonder if the PH guys have ideas on this one.

Audi V6 TDi, 85000 miles. This runs like a sewing machine, goes well, good on fuel. FSH and I have changed the oil for Castrol Edge LL 5w30 as recommended.

I get a 2 second chain rattle on a warm restart if the car has been left for a few minutes, maybe the hydraulic tensiones not holding oil ?

But it never does it on a cold start - this confuses me. If the oil has left the tensioners when it's warm, why doesnt it give a rattle when I start it the next morning ??

Maybe because the smaller amount of oil left in them is thicker ??

It didn't do this when I bought it a year ago (only done 7k miles in it since then), could the previous owner / dealer filled it with thicker oil ??

Strange one - ideas welcomed please

[slybunda]

what type of oil filter is it? if its a spin on canister type then the anti-drainback valve in it is probably not good.

[unclegrouch]

not a canister filter. would the anti drain cause the timing chain tensioners to let go of the oil ?

[GreenV8S]

Just a guess, but I suspect the timing chain is relatively stiff and not inclined to flap around much when covered in thick cold oil. When hot, the anti-drain valve in the filter is allowing the oil system to drain and it takes the pump a few seconds to fill it, build up enough pressure to start filling the chain tensioner and the chain tensioner to then take up the slack.

[unclegrouch]

interesting idea there & it sounds likely - thanks

I will look into this anti-drain valve, if it's the problem it may be an easy cure

Edited by unclegrouch on Tuesday 15th September 19:57